Process for purification of 2-chloro-5-chloromethyl-1,3-thiazole

ABSTRACT

The present invention provides a process for purifying 2-chloro-5-chloromethyl-1,3-thiazole represented by the formula (I): 
                         
characterized in that a crude 2-chloro-5-chloromethyl-1,3-thiazole represented by the formula (I) is treated with a lower alcohol before the distillation, and then is distilled. The present purification process is a new one for purifying 2-chloro-5-chloromethyl-1,3-thiazole, suitable for industrial practice.

This application is a U.S. national stage of International ApplicationNo. PCT/JP2005/004181 filed Mar. 10, 2005.

TECHNICAL FIELD

The present invention relates to a new process for purifying2-chloro-5-chloromethyl-1,3-thiazole.

BACKGROUND ART

2-Chloro-5-chloromethyl-1,3-thiazole (hereinafter, abbreviated as CCT insome cases) is an important compound as an intermediate for producingbiologically active compounds such as pesticides (see Patent Literature1: JP-A No. 3-157308). As a typical method for preparing CCT, there hasbeen a known method of reacting 2-chloroallyl isothiocyanate with achlorinating agent (see Patent Literature 2: JP-A No. 4-234864). Forpurifying crude CCT prepared by the said method, the following methodshave previously been known.

The above Patent Literature 2 has described a method of simplydistilling under reduced pressure without performing a pretreatment fordecomposing impurities present. The method requires attentions in termsof equipment and time, based on the necessity of setting a reflux ratioto obtain CCT in high purity, because the impurities are azeotropic withCCT. In other words, there is a problem of difficulty to suppress thecontent of azeotropic impurities present, when the distillation isperformed under the whole distilling conditions without a reflux ratio.There is an additional problem that the azeotropic impurities haverelatively high melting point and thus are condensed within adistillation equipment system, and the condensed impurities fixed in theequipment piping promote corrosion on the equipment, when thedistillation is performed under the whole distilling conditions withouta reflux ratio. Whereas, a problem arises that even when setting areflux ratio to suppress contamination of the impurities, the period ofdistillation is prolonged, and distillation recovery of CCT is decreaseddue to low thermal stability of CCT. This tendency is naturally strongerwith more increased charge per batch.

To solve the problems of the above purification method, PatentLiterature 3 (JP-A No. 9-316062) has proposed a method ofrecrystallizing crude CCT using an organic solvent. This method,however, requires a large amount of solvent for crystallization,resulting in an expensive material cost. Further, the method requiresequipments such as filters for crystal separation and filtrationprocessing, resulting in an expensive cost of equipments. Moreover,since the resultant crystal has a melting point of 30° C., the methodrequires an equipment for controlling a filtration temperature duringthe separation of the crystal after the crystallization, resulting in afurther cost of equipments and complicated processing operation. Inaddition, since the resultant crystal has harmful properties such as badodor, and eye or skin irritation, it is undesirable to use a filterrequiring a periodical maintenance such as replacing work of a filterfabric. Therefore, it is hard to say that the purification method byrecrystallization is a really excellent one for industrial purification.

Under such a situation as described above, there is a need for a methodof purifying CCT, which is less expensive, has good operability, and canrecover CCT in high purity and high recovery.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The object of the present invention is to provide a new process forpurifying CCT, suitable for industrial practice.

Means for Solving the Problem

As a result of the extensive investigation to solve the problemsmentioned above, the present inventors have found that, uponpurification of 2-chloro-5-chloromethyl-1,3-thiazole by distillation ofa crude product thereof, by treating the crude product with a loweralcohol before the distillation, purified CCT can be obtained in highpurity and high recovery without a specific reflux ratio and an extradistillation equipment during the distillation, and have accomplishedthe present invention.

That is, the present invention is:

-   (1) a process for purifying 2-chloro-5-chloromethyl-1,3-thiazole    represented by the formula (I):

by distillation of a crude product thereof, comprising treating thecrude product with a lower alcohol before the distillation;

-   (2) the process for purifying 2-chloro-5-chloromethyl-1,3-thiazole    according to the above (1), wherein the treatment with the lower    alcohol is carried out by adding the lower alcohol to the crude    product of 2-chloro-5-chloromethyl-1,3-thiazole, followed by    stirring;-   (3) the process for purifying 2-chloro-5-chloromethyl-1,3-thiazole    according to the above (1) or (2), wherein the crude product of    2-chloro-5-chloromethyl-1,3-thiazole is a reaction mixture or a    residue obtained by distilling the solvent from the reaction    mixture, wherein the reaction mixture is obtained by reacting a    2-halogenoallyl isothiocyanate represented by the general formula    (II):

(wherein Hal represents a chlorine atom or a bromine atom) with achlorinating agent in the presence of a solvent;

-   (4) the process for purifying 2-chloro-5-chloromethyl-1,3-thiazole    according to the above (3), wherein the crude product of    2-chloro-5-chloromethyl-1,3-thiazole is a residue obtained by    distilling the solvent from the reaction mixture;-   (5) the process for purifying 2-chloro-5-chloromethyl-1,3-thiazole    according to any one of the above (1) to (4), wherein the lower    alcohol is methanol; and-   (6) the process for purifying 2-chloro-5-chloromethyl-1,3-thiazole    according to any one of the above (3) to (5), wherein Hal is a    chlorine atom.

Effects of the Invention

According to the purification process of the present invention, crudeCCT can be purified with a simple equipment under good operableconditions in a short time, and CCT can be obtained in high purity andhigh yield.

More specifically, since the purification process of the presentinvention surprisingly can convert impurities present in CCT into acompound not being azeotropic on distillation, the distillation can beperformed without a reflux ratio, which has previously been set, inorder to separate the impurities. Further, since no azeotropicimpurities become present in CCT, the content of impurities in CCT afterthe distillation is markedly decreased. That is, highly pure CCT can beobtained in good distillation recovery.

Therefore, the purification process of the present invention can beperformed without requiring the reflux ratio to be set in order toseparate azeotropic impurities, and thus can reduce a cost of equipmentsfor reflux piping such as rectifying columns and condensers. Inaddition, since the process can be performed without requiring thereflux ratio to be set, highly purified CCT can be obtained in a shortertime. The problem that impurities azeotropic with CCT are condensedwithin a distillation equipment system, and the condensed impuritiesfixed in the equipment piping system promote corrosion on the equipment,when the distillation is conducted under the whole distilling conditionswithout setting the reflux ratio in the purification process by simplydistilling under reduced pressure without performing a pretreatment fordecomposing impurities present is solved. Further, the purificationprocess of the present invention has advantages capable of beingpracticed process using a large amount of solvent in a recrystallizationprocess and without requiring an equipment for solid-liquid separationsuch as a filter. The purification process of the present invention isof course an advantageous purification process compared to theconventional method in a small scale, but dramatically exerts a moreeffect with a larger amount of charge.

BEST MODE FOR CARRYING OUT THE INVENTION

The crude product of CCT, to which the purification process of thepresent invention can be applied, is not specifically limited, butpreferably is a reaction mixture or a residue obtained by distilling thesolvent from the reaction mixture, wherein the reaction mixture isobtained by reacting 2-halogenoallyl isothiocyanate represented by theformula (II) with a chlorinating agent in the presence of the solvent.The reaction of the compound represented by the formula (II) with thechlorinating agent is conducted according to the methods such as JP-ANo. 4-234864 and JP-A No. 2002-255948. The chlorinating agent as usedherein refers chlorine and compounds releasing chlorine under thereaction conditions (such as sulfuryl chloride and phosgene). Examplesof the solvent include, but not limited to, toluene, o-xylene, m-xylene,p-xylene, chlorobenzene, dichlorobenzene, dichloromethane, chloroform,1,2-dichloroethane, carbon tetrachloride, acetonitrile and the like.

The purification from the crude product can be performed by treating thecrude product with a lower alcohol and then distilling, and thetreatment with the lower alcohol is preferably performed by adding thelower alcohol to the crude product, followed by stirring.

Examples of the lower alcohol used in the present invention include C₁₋₆alcohols such as methanol, ethanol, propanol, isopropyl alcohol,butanol, isobutanol, sec-butanol, tert-butanol, pentanol, hexanol, amongwhich methanol is particularly preferable.

The addition amount of the lower alcohol is usually 0.001 to 1 part byweight, preferably 0.01 to 0.1 part by weight, particularly preferably0.01 to 0.05 part by weight to 1 part by weight of 2-halogenoallylisothiocyanate as a starting material.

The adding time of the lower alcohol is not specifically limited as longas it is after the reaction of 2-halogenoallyl isothiocyanate as astarting material with the chlorinating agent has been completed toproduce CCT, and may be before or after separation of the reactionsolvent by the methods such as distillation under reduced pressure.Specifically, the lower alcohol may be added after the reaction has beencompleted to produce CCT, or may be added to a concentrated residueobtained by concentrating the reaction mixture after the reaction thathas been completed to produce CCT, under reduced pressure to remove thereaction solvent. From the viewpoint of the industrial practice, amethod in which the lower alcohol is added after recovering a reactionsolvent has an excellent characteristic that the reaction solvent can bereused. After addition of the lower alcohol, a mixture is stirred.

The temperature of adding the lower alcohol and that of stirring afterthe addition can be varied within the relatively wide range. Generally,these adding and stirring temperatures are, usually 0° C. to 100° C.,preferably 10° C. to 80° C., more preferably 20° C. to 60° C. Thestirring period after the addition of the lower alcohol is usually 10minutes to 4 hours, preferably 30 minutes to 2 hours.

Treatment with the lower alcohol may be performed under reduced orincreased pressure, but is usually performed under atmospheric pressure.

Distillation after the treatment with the lower alcohol may be performedunder the whole distilling conditions without refluxing after aningredient having low boiling point is fractionated as an initialdistillate, and thereby CCT can be obtained as a main distillate. Thedistillation is performed within the temperature range in which CCT andthe distillation residue are not thermally decomposed. Specifically, thedistillation is performed usually not more than 200° C., preferably notmore than 124° C. of temperature inside the distiller. The distillationis also performed usually not more than 10 kPa, preferably not more than3 kPa of pressure inside the distiller.

EXAMPLES

The present invention is further described in detail by the followingExamples, but not limited by those Examples in any way.

Example 1

A mixture of 1022 kg of 2-chloroallyl isothiocyanate and 1298 kg oftoluene was heated to 45° C., and was added dropwise with 1095 kg ofsulfuryl chloride over 3 hours. The mixture was stirred at 45° C. for 2hours and further stirred at 80° C. for 1 hour, and then heated underreduced pressure, and thereby 1169 kg of toluene was distilled off andrecovered. The concentrated residue was cooled to 39° C., and then addedwith 22 kg of methanol. The mixture was stirred at 60° C. for 1 hour,and then distilled to fractionate 128 kg of initial distillate.Distillation under reduced pressure (whole distilling conditions: refluxratio for the main distillate is 0, pressure inside the distiller: 0.7to 1.0 kPa, top temperature: 71 to 95° C.) was further performed for 18hours to give 956 kg of CCT in 98.3% purity (yield: 78%).

Example 2

A mixture of 1000 kg of 2-chloroallyl isothiocyanate and 1297 kg oftoluene was heated to 45° C., and was added dropwise with 1071 kg ofsulfuryl chloride over 3 hours. The mixture was stirred at 45° C. for 2hours and further stirred at 80° C. for 1 hour, and then heated underreduced pressure, and thereby 1169 kg of toluene was distilled off andrecovered. The concentrated residue was cooled to 38° C., and then addedwith 22 kg of methanol. The mixture was stirred at 60° C. for 1 hour,and then distilled to fractionate 120 kg of initial distillate.Distillation under reduced pressure (whole distilling conditions: refluxratio for the main distillate is 0, pressure inside the distiller: 0.5to 1.6 kPa, top temperature: 72 to 91° C.) was further performed for 18hours to give 970 kg of CCT in 98.3% purity (yield: 81%).

Comparative Example 1

A mixture of 1066 kg of 2-chloroallyl isothiocyanate and 1297 kg oftoluene was heated to 45° C., and was added dropwise with 1131 kg ofsulfuryl chloride over 3 hours. The mixture was stirred at 45° C. for 2hours and further stirred at 80° C. for 1 hour, and then heated underreduced pressure, and thereby 1170 kg of toluene was distilled off andrecovered. 101 kg of initial distillate was fractionated from theconcentrated residue. Distillation under reduced pressure (wholedistilling conditions: reflux ratio for the main distillate is 0,pressure inside the distiller: 0.8 to 1.3 kPa, top temperature: 71 to88° C.) was further performed for 23 hours to give 964 kg of CCT in91.4% purity (yield: 70%).

Comparative Example 2

A mixture of 1021 kg of 2-chloroallyl isothiocyanate and 1296 kg oftoluene was heated to 45° C., and was added dropwise with 1092 kg ofsulfuryl chloride over 3 hours. The mixture was stirred at 45° C. for 2hours and further stirred at 80° C. for 1 hour, and then heated underreduced pressure, and thereby 1114 kg of toluene was distilled of f andrecovered. 82 kg of initial distillate was fractionated from theconcentrated residue. Distillation under reduced pressure (purificationconditions: reflux ratio for the main distillate is (refluxingamount/distilled amount)=(25/120 for the first half) turned to (70/70for the last half), pressure inside the distiller: 1.1 to 1.5 kPa, toptemperature: 80 to 90° C.) was further conducted for 45 hours to give911 kg of CCT in 98.0% purity (yield: 74%).

INDUSTRIAL APPLICABILITY

According to the purification process of the present invention, highlypurified 2-chloro-5-chloromethyl-1,3-thiazole can be obtained in highyield with a simple equipment under good operable conditions in a shorttime. Therefore, the purification process of the present invention isextremely useful industrially.

1. A process for purifying 2-chloro-5-chloromethyl-1,3-thiazolerepresented by the formula (I):

which consists essentially of: treating a crude2-chloro-5-chloromethyl-1,3-thiazole represented by the formula (I) witha lower alcohol, and then distilling the treated2-chloro-5-chloromethyl-1,3-thiazole.
 2. The process for purifying2-chloro-5-chloromethyl-1,3-thiazole according to claim 1, wherein thecrude 2-chloro-5-chloromethyl-1,3-thiazole is treated with the loweralcohol by adding the lower alcohol to the crude2-chloro-5-chloromethyl-1,3-thiazole, followed by stirring.
 3. Theprocess for purifying 2-chloro-5-chloromethyl-1,3-thiazole according toclaim 2, wherein the lower alcohol is methanol.
 4. The process forpurifying 2-chloro-5-chloromethyl-1,3-thiazole according to claim 1,wherein the crude 2-chloro-5-chloromethyl-1,3-thiazole is a reactionmixture obtained by reacting a 2-halogenoallyl isothiocyanaterepresented by the general formula (II):

wherein Hal represents a chlorine atom or a bromine atom, with achlorinating agent in the presence of a solvent, or wherein the crude2-chloro-5-chloromethyl-1,3-thiazole is a residue obtained by distillingthe solvent from the reaction mixture.
 5. The process for purifying2-chloro-5-chloromethyl-1,3-thiazole according to claim 4, wherein thecrude 2-chloro-5-chloromethyl-1,3-thiazole is a residue obtained bydistilling the solvent from the reaction mixture.
 6. The process forpurifying 2-chloro-5-chloromethyl-1,3-thiazole according to claim 5,wherein the lower alcohol is methanol.
 7. The process for purifying2-chloro-5-chloromethyl-1,3-thiazole according to claim 6, wherein Halis a chlorine atom.
 8. The process for purifying2-chloro-5-chloromethyl-1,3-thiazole according to claim 5, wherein Halis a chlorine atom.
 9. The process for purifying2-chloro-5-chloromethyl-1,3-thiazole according to claim 4, wherein thelower alcohol is methanol.
 10. The process for purifying2-chloro-5-chloromethyl-1,3-thiazole according to claim 9, wherein Halis a chlorine atom.
 11. The process for purifying2-chloro-5-chloromethyl-1,3-thiazole according to claim 4, wherein Halis a chlorine atom.
 12. The process for purifying2-chloro-5-chloromethyl-1,3-thiazole according to claim 1, wherein thelower alcohol is methanol.